Whale watchers consider spotting a killer whale off the Oregon coast something of a rarity. But how’s this for an impressive sighting: scientists at the University of British Columbia may have identified a previously unknown subset of orcas active in the open ocean beyond Oregon’s coastline, according to a study recently published in the scientific journal Aquatic Mammals.

“It’s pretty unique to find a new population,” says co-author Dr. Andrew Trites, professor at the UBC Institute for the Oceans and Fisheries. Just about 2,500 of the world’s 50,000 orcas call the northeastern Pacific Ocean home, per the National Oceanic and Atmospheric Administration—among them the famously endangered southern residents, who forage at the mouth of the Columbia River. 

Scientists first photographed around 35 unknown orcas attacking a pod of sperm whales off the coast of California in 1997. Since then, researchers, whale watchers, birders, and fishermen have documented nine encounters with 49 total unidentified killer whales. Waters off the Oregon coast played host to three official sightings, including in 2015, when NOAA researchers watched nine orcas attack an elephant seal about 300 kilometers west of Newport.

The study spares no clinical detail in describing the group’s kills—in part because their diet separates them from the two killer whale “ecotypes” known to inhabit waters beyond the continental shelf. The offshore killer whale ecotype lives in deeper oceanic waters, feeding on sharks and large fish. Transient killer whales feed on mammals, but tend toward coastal waters.

The new group lives in depths similar to the offshore type, but like the transient type, eats mammals—including sperm whales, which have never been documented prey for Oregon and California’s transient killer whales.

Their physical attributes don’t align perfectly with any known ecotype, either. The whales described in the study have unique and varied dorsal fins and back patches, as well as distinctive cookie-cutter shark bite scars, indicating that they live in deep, open waters. 

Determining whether they’re a subtype of an existing group or a new ecotype of their own will require further research. In the meantime, Oregonians can add another white whale to their list.